This invention relates to a system for heating of the interior of a motor vehicle as claimed in the preamble of claim 1.
One problem in conventional motor vehicle heating systems in which hot air is produced by heat exchange with the engine coolant consists in that after starting the engine a certain time interval is necessary for the coolant to become hot enough to perform a heating function. DE 44 33 81 A1 discloses a generic heating system in which an additional electrical heating element which is formed by a metal tube is integrated into the coolant circuit. The jacket surface of the tube is in direct contact with PTC heating elements which are supplied with electricity from the vehicle electrical system to heat the tube and thus also the coolant flowing through the tube independently of the heat supply by the motor vehicle engine.
DE 197 19 487 A1 proposes that a heating vessel which is provided with a microwave source to heat coolant independently of the vehicle engine be integrated into the coolant circuit of the motor vehicle.
The defect in this known heating system is the fact that providing additional water heaters entails high installation cost and high installation space requirement.
The object of this invention is to devise a heating system which allows heating of the liquid in the coolant circuit independently of the engine and does not entail high installation effort and installation space requirement.
This object is achieved as claimed in the invention by a heating system as is defined in claim 1. In this approach as claimed in the invention it is advantageous for the electrical heating device to be integrated into a component of the coolant circuit which is present anyway so that the installation cost and the installation space requirement for this coolant heating independent of the engine can be kept low.
Preferred embodiments of the invention are given in the dependent claims.
In motor vehicles with water-cooled engines, in the coolant circuit there is conventionally at least one valve block to control the coolant flow conventionally depending on the temperature of the coolant or the pressure. This invention is aimed at integrating an electrical heating device into this valve block to heat the coolant flowing through the valve block. Since in this way additional electrical heating is integrated into a component which is present anyway, no additional installation space is required and installation is kept simple; this keeps costs low. The heating device is preferably one or more PTC (positive temperature coefficient) heating elements which are in direct thermal contact with the valve block in order to heat it. The heating elements can be located on the outside of the valve block. The heating elements are supplied with electricity from the vehicle electrical system, the wiring preferably being chosen such that the heating elements are supplied with electricity only with the generator running, in order to prevent discharge of the vehicle battery.
After starting the engine, thus faster heating of the coolant can be achieved by means of the additional electrical heating device in the coolant valve block, enabling faster heating of the motor vehicle interior.
The system control is preferably designed such that when a heat exchange medium is being heated (for example by the operation of an internal combustion engine or an additional motor vehicle heater) the electrical heat output is reduced accordingly or completely stopped.